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- Variation of the giant intrinsic spin Hall conductivity of Pt with carrier lifetime. [Journal Article]Sci Adv 2019; 5(7):eaav8025SA
- More than a decade after the first theoretical and experimental studies of the spin Hall conductivity (SHC) of Pt, both its dominant origin and amplitude remain in dispute. We report the experimental determination of the rapid variation of the intrinsic SHC of Pt with the carrier lifetime (τ) in the dirty-metal regime by incorporating finely dispersed MgO intersite impurities into the Pt, while m…
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- Operator Size at Finite Temperature and Planckian Bounds on Quantum Dynamics. [Journal Article]Phys Rev Lett 2019; 122(21):216601PR
- It has long been believed that dissipative timescales τ obey a "Planckian" bound τ≳(ℏ/k_{B}T) in strongly coupled quantum systems. Despite much circumstantial evidence, however, there is no known τ for which this bound is universal. Here we define operator size at a finite temperature, and conjecture such a τ: the timescale over which small operators become large. All known many-body theories are…
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- Effects of chaotic dynamics on quantum friction. [Journal Article]Phys Rev E 2019; 99(4-1):042214PR
- By means of studying the evolution equation for the Wigner distributions of quantum dissipative systems we derive the quantum corrections to the classical Liouville dynamics, taking into account the standard quantum friction model. The resulting evolution turns out to be the classical one plus fluctuations that depend not only on the ℏ size but also on the momentum and the dissipation parameter (…

- Exceptionally High, Strongly Temperature Dependent, Spin Hall Conductivity of SrRuO3. [Journal Article]Nano Lett 2019; 19(6):3663-3670NL
- Spin-orbit torques (SOT) in thin film heterostructures originate from strong spin-orbit interactions (SOI) that, in the bulk, generate a spin current due either to extrinsic spin-dependent, skew, or/and side-jump scattering or to intrinsic Berry curvature in the conduction bands. While most SOT studies have focused on materials with heavy metal components, the oxide perovskite SrRuO3 has been pre…
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- Upper Bound to the Orbital Angular Momentum Carried by an Ultrashort Pulse. [Journal Article]Phys Rev Lett 2019; 122(12):123904PR
- Photons in a ring-shaped vortex light beam can have an arbitrarily high orbital angular momentum (OAM) lℏ, in addition to the spin angular momentum ±ℏ. For a pulsed vortex beam, there is, however, an upper bound to the integer units l of OAM, or topological charge of the vortex, and a lower bound to the pulse duration to carry OAM. These limits have implications in experiments with ultrashort vor…
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- Giant intrinsic spin Hall effect in W3Ta and other A15 superconductors. [Journal Article]Sci Adv 2019; 5(4):eaav8575SA
- The spin Hall effect (SHE) is the conversion of charge current to spin current, and nonmagnetic metals with large SHEs are extremely sought after for spintronic applications, but their rarity has stifled widespread use. Here, we predict and explain the large intrinsic SHE in β-W and the A15 family of superconductors: W3Ta, Ta3Sb, and Cr3Ir having spin Hall conductivities (SHCs) of -2250, -1400, a…
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- Thermal Emission from Semiclassical Dynamical Systems. [Journal Article]Phys Rev Lett 2019; 122(10):101603PR
- Recently the bound on the Lyapunov exponent λ_{L}≤2πT/ℏ in thermal quantum systems was conjectured by Maldacena, Shenker, and Stanford. If we naïvely apply this bound to a system with a fixed Lyapunov exponent λ_{L}, it might predict the existence of the lower bound on temperature T≥ℏλ_{L}/2π. Particularly, it might mean that chaotic systems cannot be zero temperature quantum mechanically. Even c…
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- Pair-Breaking Collective Branch in BCS Superconductors and Superfluid Fermi Gases. [Journal Article]Phys Rev Lett 2019; 122(9):093403PR
- We demonstrate the existence of a collective excitation branch in the pair-breaking continuum of superfluid Fermi gases and BCS superconductors. At zero temperature, we analytically continue the equation on the collective mode energy in Anderson's Random Phase Approximation or Gaussian fluctuations through its branch cut associated with the continuum, and obtain the full complex dispersion relati…
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- Exponentially fast dynamics of chaotic many-body systems. [Journal Article]Phys Rev E 2019; 99(1-1):010101PR
- We demonstrate analytically and numerically that in isolated quantum systems of many interacting particles, the number of many-body states participating in the evolution after a quench increases exponentially in time, provided the eigenstates are delocalized in the energy shell. The rate of the exponential growth is defined by the width Γ of the local density of states and is associated with the …

- Heat transfer statistics in mixed quantum-classical systems. [Journal Article]J Chem Phys 2018; 149(22):224104JC
- The modelling of quantum heat transfer processes at the nanoscale is crucial for the development of energy harvesting and molecular electronic devices. Herein, we adopt a mixed quantum-classical description of a device, in which the open subsystem of interest is treated quantum mechanically and the surrounding heat baths are treated in a classical-like fashion. By introducing such a mixed quantum…
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